Process of lubrication



United States Patent PROCESS or LUBRICATION John A. Henricks, Baltimore, Md., assignor to Devex Corporation, Lakewood, Ohio, a corporation of Ohio No Drawing. Application November 14, 1951 Serial No. 256,374 I 8 Claims. (Cl. 117- -97) This invention relates to the lubrication of sliding metal sources. It particularly relates-to the lubrication of surfaces under conditions of extreme pressureor temperature as encountered in ordnance projectiles,-internal combustion engines, gas turbines and the like.

In the lubrication of worked metallic surfaces/such as in the forming of metals by deep drawing or stamping, an intermittent thrusting friction is encountered. Lubrieating compositions designed for intermittent friction generally are not satisfactory for relatively continuous uniform friction such as that encountered in gas turbines and the like.

It is therefore an object of the present invention to provide a lubricating process which is satisfactory for use with intermittent frictional conditions and constant frictional conditions at elevated temperatures.

It is an object of the present invention to provide a lubricating composition which is effective for use with relatively continuous uniform friction at elevated temperatures.

In accordance with one aspect of the present invention, I provide in a fixed film between the surfaces to be subjected to friction a solid material which melts at a temperature substantially below the melting point of the lower melting'metal but above room temperatures and preferably above temperatures where hydrocarbon compounds are stable, and which has a hardness substantially below the hardness of the metal being worked. A plurality of such solid materials of distributed melting points and disposed within a vehicle containing a suitable organic binder may be used to obtain further improvements. Preferably a plurality of fusible layers containing materials which melt or are liquids at different temperatures is used with the highest melting directly on the surface of the metal to be Worked. i

A stepwise lubrication of the metal surface'sby the use of a plurality of meltable or fusible materials which have a hardness below that of the metal being worked and which are lubricants at dilferentteinperatures below the melting point of themetal being worked, or which form lubricants below the melting pointof the material being worked, so that at all times when themetal is being subjected tohigh friction, regardless of the temperature, lubrication and cooling is present to prevent galling,

welding'or seizure of the relatively moving metal parts.

The plurality. of meltable or fusible materials is preferably applied as a coating over the metal which maybe in the clean or pickled state or which as is, preferable may be provided with the adherent integral coating of a meltable substance such as a low-melting ferrous sulfide or phosphate (preferably an iron compound) formed in situ thereon, as by chemical reaction, enameling, plating, etc.

Anotherv method suitable for forming the integral procedure set forth in the Montgomery U. SQPatent No.

2,366,208 isto form a ferrous sulfide layerv on steel in an aqueous media 'such'as a solution of sodium thio- Water soluble sulfurizing lubricant Parts Diethyleneglycolor sodium stearate 20 Starch or polyvinyl alcohol 10 Boric acid (or monosodium phosphate, 60 parts) Sodium thiosulfate, or sodium tetrathionate 4 1 60 parts of monosodium phosphate is substantially equal molar to 30 parts of boric acid.

The foregoing dry mixture is dissolved in warm water at a concentration of from 4 to 32 ounces per gallon, and the bath heated to boiling after which the articles to be treated are immersed in the hot solution for'about five minutes during which time the ferrous surface is blackened by the formation of ferrous sulfide. The film remaining on the work is itself a stepwise lubricant by virtue of the fusible and polar stearate and the fusible boric acid or monosodium phosphate contained in the formulation.

"to be drawn or formed. The black hexagonal ferrous sulfide on the surface of the metal to be cold worked facilitates drawing operations and even permits successful drawing of many articles without an additional lubricating coating. If the surface containing the integrally formed ferrous sulfide is'no-t drawn immediately, or ifit is allowedto remain for any substantial time in an oxidizing atmosphere, a'protective coating such for example as a wax or resin solution or other impervious covering should be applied to prevent formation of harder and higher melt-.

ing materials. a

Superior results, as above mentioned, are obtained,

however, when the Wearing surface such as that of a metal workpiece is treated or coated with a fixed film of composition comprising essentially one or more esters of glass forming acids,'having a hardness on the Mohsscale of less than 5 (preferably less than 4). and having a} melting point less than the melting point of the metal to be worked (preferably less than 1150" C. or, 1200 C.), and a suitable vehiclein which said esters is insoluble.

Such a composition generally permits: satisfactory cold.

working or drawing without treatment of the metal to form an adherent, integral sulfide thereon. Such'a com;

position provides excellentlubrication for constant sliding friction such as encountered in internal combustion engines." t Y p T he vehicleusually comprises a binding material (preferably a fusible resinous material) and a'suitable volatile solvent or agent adapted to impart the required fluiditv to n the composition. 7 1- While the compositions to the present invention are adapted for the drawing or working ofmetals, they are preferably suitablefor the lubrication of elements subjected to severe friction, particularly'those subjected to frictionat high temperatures such as may be encountered in ordnance projectiles, gas turbines, internal combustion engines or the like with or ,withoutfirst forming an intelubricants, solutions of meltable glass forming pigments also, function very satisfactorily and sometimes have a desirable effect. Thus oil insoluble esters of glass forming acids such as boric and phosphoric esters are highly desirable as coolants and lubricants ininternal combustion orgas reaction turbine engines or the like. The glass forming acids such as boric, phosphoric, and arsenic or their salts particularly alkali metal salts may also be used in gas reaction turbines as lubricants and coolants of blade surfaces, etc. Water soluble polyhydric, alcohol esters of glass forming acids such glycerol borates and phosphates, glycol borates and phosphates, etc., are especially desirable as lubricants for sliding friction either when incorporated in a fuel, or separately as an ester, or in Water solution. Such solutions of esters may also be pigmented with a fusible element such as aluminum stearate as having a scratch hardness below 5 on Mohs scale. In any case the lubricating compositions should be free of materials which break down under heat to providev ingredientshaving a scratch hardness greater than 5, or which in themselves have a scratch hardness greater than 5.

I have also discovered that porous materials such as hearings or materials made of powdered or sintered powdered metal and surfaces plated with porous chromium have greatly reduced frictional tendency over long periods when they are impregnated with esters of glass-forming acids, such as phosphoric, boric and arsenic acids. These esters, which preferably are water-soluble polyhydric alochol esters of glass-forming acids, and therefore, oilinsoluble remain within the pores of the chromium surface to give reduced friction under even abnormal conditions, such as are encountered in the stressing or drawing of metal or in internal combustion engines. Cylinders' of internal combustion engines impregnated with one or more such esters have exceptional wear resistance and low friction properties.

These glass-forming esters or their solutions or dispersions may be pigmented with the meltable pigments as aforementioned and may be applied as aqueous solutions to impregnate the porous chromium surface. A surface-active agent such as a soap or wetting agent may also be present. Of the glass-forming esters, glycol borate is exceptional and especially desirable as it has low cost and is very effective. Other polyhydric alcohol esters such for example as the cellulose, glucose, and starch esters of the glass-forming acids may also be used with great effectiveness.

Since cooling is a very important function of a lubricant, any physical or chemical reaction that takes up heat is a valuable addition to stepwise lubrication. For instance, the glyceryl borate resins cited in Example 1 could be made in situ by frictional heat if an aqueous solution of glycerine and boric acid were used as a lubricant. Thus, in a metal cutting or grinding operation I can use such an unpolymerized solution as the coolant andform the protective resin only at points of extreme heat and pressure.

Binders natural or synthetic resin having a melting or softening point below 300 C. The choice of vehicles and pigments is usually determined by the expenditure that can be made and the severity of service required. When the service is not so severe and the expediture is limited, a heatlabile binding material such as the organic colloids which decompose at relatively low temperatures may be used and the principal reliancefor lubrication all based upon the fusible pigments. On the other hand, when there is severe service and suitable expenditures can be made, a fusible natural, synthetic or resinous material is preferred.

Perhaps the most significant difierence between this invention and the prior art lubricants lies in the cooling action of these novel lubricants. The only cooling action of the prior artlubricants is in their heat of vaporization as they boil off of the over-heated surfaces, and their heat exchange cooling as they are circulated between the moving surfaces and a reservoir or oil sump. These novel lubricants, however, utilize the heat of fusion of a fusible pigment to" cool the frictional surfaces. The use of fusible cooling pigments eliminates the lapping action and heat generation-of the infusible prior art filler type pigments. Another valuable gain is the protective action of the :fusible pigments upon the thermoplastic organic binders which would otherwise be decomposed by the frictional heat. For example, low carboniron rod was drawn with a coating of sodium stearate asthe lubricant, which drawing left a charred carbonized film on the rod. When, however, the same type rod was coated with a sodium stearate film containing a fusible borate, the residual soap film was darkened but not carbonized by thefrictional heat.

The following example illustrates this aspect of my invention:

Example 1 The porous chromium plated cylinder bores of a diesel engine are impregnated by swabbing with a hot aqueous solution containing six ounces per gallon ofv a glyceryl borate resin and 1 ounce per gallon of diethyl glycol stearate. The coating-is dried with an air blast. Atest run of the engine thus heated, showsless weight loss from the piston rings than does a similar run using: identical cylinders without the glyceryl borate impregnation. When porous bearings (prepared from sintered. metal powder) are impregnated with water-soluble esters of a glass-forming acid and a water-soluble fatty acid ester of a polyhydric alcohol, satisfactory lubricationis also obtained;

In internal combustion engines, it is advisableto maintain the film on the cylinder borerby using a boric acid ester such as ethyl borate as a component of the fuel or the lubricating oil, or to use an aqueoussolution of glyceryl borate as a water injection fluid. The same system of coating the combustion chamber walls with a boric or phosphoric acid ester and then maintaining such a protective film by incorporating a glassv forming ester as a fuel or lubricating oil ingredient or'using an aqueous- A steel piston for a gasoline engine is cleaned inv an alkaline cleaner and then givena copper immersion coating in a solution of.2 oz. per gallon copper sulfate and 1 oz. per gallon sulfuric acid. After rinsing the immersion copper plate is wiped with a solution of 5%phosphoric acid containing a wetting agent to form a thin film of copper phosphate on. the coating so that the copper will not subsequently react with the lubricating oils. The piston is then impregnated with a film of glyceryl borate in the manner described in Example 1. The piston is then installed in a gasoline engine Where'it is found that this treatment of'the piston appears to prevent the piston rings from sticking or freezing to the piston ring grooves during prolonged .operation.

It should be clear fromthese examples thatI am able to provide adequate stepwise lubrication for all cases involving sliding friction by providing fusiblesecondary lubricants in addition to the initialor primary-lubrication. In cases involving extreme pressures and high frictional heats I prefer to make thesecondary lubricant an integral part of the sliding metal by electroplating, chemically reacting, or enameling the secondary lubricant on the sliding metal surface. By this preferred means I have a fusible barrier film that will still prevent welding and galling between sliding surfaces where the fluids melted thermoplastic primary lubricant has been squeezed out of the sliding junction.

This application is a continuation-in-part application of my copending application Serial Number 665,905 filed April 29, 1946, now abandoned.

It is also apparent that modifications of the invention may be made without changing the spirit thereof, and it is intended that the invention be limited only by the appended claims.

What I claim is:

1. A method of lubricating metal surfaces of internal combustion engines that are subjected to substantially continuous dry sliding solid-on-solid friction over long periods of time at elevated temperatures above the stability of hydrocarbon lubricating oils, which comprises introducing upon a wearing surface of said engine during operation an ester of glycerol and boric acid.

2. A method of lubricating metal surfaces of internal combustion engines that are subjected to substantially continuous dry sliding solid-on-solid friction over long periods of time at elevated temperatures above the stability of hydrocarbon lubricating oils, which comprises introducing upon a wearing surface of said engine during operation an ester of glycol and boric acid.

3. A porous metal surface containing in pores adjacent the surface thereof a water-soluble, oil insoluble ester of glycerol and boric acid.

4. A porous metal surface containing in pores adjacent the surface thereof ethyl borate and glycerol borate.

5. A method of lubricating metal surfaces of internal combustion engines that are subject to a substantially uniform continuous sliding friction, comprising introducing upon a porous Wearing surface a polyhydric alcohol selected from a member of the group consisting of glycerol, glycol, glucose, starch and cellulose, introducing a glass forming acid selected from a member of the group consisting of boric, arsenic and phosphoric upon said wearing surface, and thereafter forming a lubricating film in situ upon said wearing surface.

6. A method of lubricating metal surfaces of internal combustion engines that are subject to a substantially uniform continuous sliding friction, comprising introducing upon a porous wearing surface glycerine, introducing a boric acid upon said surface, and thereafter forming a lubricating film in situ upon said wearing surface.

7. A method of lubricating metal surfaces of internal combustion engines that are subject to a substantially uniform continuous sliding friction, comprising introducing upon a porous wearing surface glucose, introducing a phosphoric acid upon said surface, and thereafter forming a lubricating film in situ upon said wearing surface.

8. A method of lubricating metal surfaces of internal combustion engines that are subject to a substantially uniform continuous sliding friction, comprising introducing upon a porous wearing surface glucose, introducing a boric acid upon said surface, and thereafter forming a lubricating film in situ upon said wearing surface.

References Cited in the file of this patent UNITED STATES PATENTS 955,592 Hemann Apr. 19, 1910 1,054,265 Baekeland Feb. 25, 1913 1,354,487 Jensen Oct. 5, 1920 1,398,775 Gerleman Nov. 29, 1921 1,409,658 Brann Mar. 14, 1922 1,462,855 Gerleman July 24, 1923 1,957,259 Gallsworthy May 1, 1934 2,031,368 Hodson Feb. 18, 1936 2,225,815 Acheson Dec. 24, 1940 2,235,161 Morway Mar. 18, 1941 2,245,649 Caprio June 17, 1941 2,258,309 Zimmer Oct. 7, 1941 2,266,377 Neeley Dec. 16, 1941 2,285,854 Downing et al. June 9, 1942 2,294,760 Morris Sept. 1, 1942 2,366,208 Montgomery Jan. 2, 1945 2,391,468 Long Dec. 25, 1945 2,449,771 Dolan Sept. 21, 1948 2,469,473 Orozco et al. May 10, 1949 2,470,136 Bramberry May 17, 1949 2,588,234 Hendricks Mar. 4, 1952 2,632,767 Smith et al Mar. 24, 1953 

5. A METHOD OF LUBRICATING METAL SURFACES OF INTERNAL COMBUSTION ENGINES THAT ARE SUBJECT TO A SUBSTANTIALLY UNIFORM CONTINUOUS SLIDING FRICTION, COMPRISING INTRODUCING UPON A POROUS WEARING SURFACE A POLYHYDRIC ALCOHOL SELECTED FROM A MEMBER OF THE GROUP CONSISTING OF GLYCEROL, GLYCOL, GLUCOSE, STARCH AND CELLULOSE, INTRODUCING A GLASS FORMING ACID SELECTED FROM A MEMBER OF THE GROUP CONSISTING OF BORIC, ARSENIC AND PHOSPHORIC UPON SAID WEARING SURFACE, AND THEREAFTER FORMING A LUBRICATING FILM IN SITU UPON SAID WEARING SURFACE. 